As shown in FIGS. 1 and 2, a prior art rack is composed of four upright support units, a plurality of horizontal support frames, and a plurality of fastening blocks for fastening the horizontal support frames with the four upright support units. Each of the horizontal support frames has four corners which are respectively fastened with a fastening block by welding. The fastening block has a retaining portion of a semicircular cross section for retaining an upright support unit. Each of the four upright support units is formed of two upright rods parallel to each other.
Such a prior art rack as described above is defective in design in that the horizontal support frames are incapable of carrying the weight of a heavy article placed thereon in light of the horizontal support frames being fastened with the fastening blocks by welding. In addition, the prior art rack cannot be easily assembled by a do-it-yourselfer.